#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

int main()
{
	double sum = 0;
	int k = 1;
	int i = 1;
	while (i <= 100)
	{
		sum += k * 1.0 / i;
		k *= -1;
		i++;
	}
	printf("%lf", sum);
	return 0;
}